The Saudi-led coalition says its aircraft have only targeted military camps, air bases, weapons depots and rebel headquarters, but civilian areas have often been hit.

The UN estimates that more than 560 people have been killed since 19 March.

Pakistan's parliament began debating involvement on Monday and many lawmakers spoke out against sending troops to Yemen.

Friday's resolution said that Pakistan should play a mediating role and backed the government's commitment to protect Saudi territory, which has so far not been threatened in the conflict.

Saudi Arabia and Yemen share a border and there are fears instability might spill into Saudi territory.

"The parliament of Pakistan expresses serious concern on the deteriorating security and humanitarian situation in Yemen and its implications for peace and stability of the region," the resolution said.

The Shia Houthi rebels are seen as being allied to Iran, a rival for power in the Middle East with Sunni-majority Saudi Arabia.

Analysts say Pakistan, which has a Sunni majority but also a Shia minority, fears being caught between the two if it sends troops to Yemen.

Earlier this week Iranian Foreign Minister Javad Zarif travelled to Pakistan to urge the country to reject the Saudi request.

Meanwhile two planes carrying medical aid landed in the capital Sanaa on Friday after days of failed attempts.

The International Committee of the Red Cross (ICRC) and the United Nation Children's Fund, UNICEF, said planes carrying more than 30 tonnes of medical supplies including medicines, bandages, intravenous drips and surgical equipment were in Sanaa.

Saudi Arabia launched the airstrikes after the Houthi rebels seized the capital, forcing President Abdrabbuh Mansour Hadi to flee to Aden, and later Riyadh.